Chromatographic separation of mixed peptides from amino acids in biological digests with volatile buffers

Development of a defined medium for the heterotrophic cultivation of Metallosphaera sedula

The heterotrophic cultivation of extremophilic archaea still heavily relies on complex media. However, complex media are associated with unknown composition, high batch-to-batch variability, potential inhibiting and interfering components, as well as regulatory challenges, hampering advancements of extremophilic archaea in genetic engineering and bioprocessing. For Metallosphaera sedula, a widely studied organism for biomining and bioremediation and a potential production host for archaeal ether lipids, efforts to find defined cultivation conditions have still been unsuccessful. This study describes the development of a novel chemically defined growth medium for M. sedula. Initial experiments with commonly used complex casein-derived media sources deciphered Casamino Acids as the most suitable foundation for further development. The imitation of the amino acid composition of Casamino Acids in basal Brock medium delivered the first chemically defined medium. We could further simplify the medium to 5 amino acids based on the respective specific substrate uptake rates. This first defined cultivation medium for M. sedula allows advanced genetic engineering and more controlled bioprocess development approaches for this highly interesting archaeon.

Silva M. Effect of Some Hydrolytic Parameters in the Action of Subtilisin and Pancreatin on Whey Protein Concentrate

In this work, the influence of some reactional parameters in the hydrolysis of whey protein concentrate (WPC) was evaluated, in terms of the nutritional quality of peptide profiles of the hydrolysates as well as the reduction of costs for scaling-up the process. Two enzymes (subtilisin and pancreatin) were used for preparing 18 hydrolysates, using different E:S ratios and reaction times, and the distribution of peptides according to chain length was analyzed by size-exclusion chromatography. The studied parameters affected the peptide profiles of WPC hydrolysates and the best result was similar for subtilisin and pancreatin, both using an E:S ratio of 4:100, after 5 h and 10 h, respectively. In these conditions, these enzymes gave rise to the smallest large peptide contents (12.28% and 12.34%, respectively) and one of the highest amount of di- and tripeptides (13.34% and 13.00%, respectively) as well as of free amino acids (45.56% and 47.26%, respectively). However, in terms of number of samples the action of pancreatin was more advantageous than subtilisin, since among the nine hydrolysates, four showed appropriate peptide profiles (P1, P2, P5, and P6), from the nutritional point of view, while the same happened only with one hydrolysate prepared by using subtilisin (S3). Also, the economical advantage of using smaller E:S ratio and reaction time was observed in several cases for both enzymes.

A defined medium for rumen bacteria and identification of strains impaired in de novo biosynthesis of certain amino acids

A completely defined growth medium has been developed to determine the nitrogen requirements for several species of ruminal bacteria, and has revealed two strains which are impaired in de novo biosynthesis of certain amino acids. Using NH4Cl as a sole nitrogen source, the medium supported growth of Butyrivibrio, Selenomonas, Prevotella and Streptococcus species. One strain of B. fibrisolvens (E14) and one strain of P. ruminicola (GA33) did not grow in the presence of NH4Cl until the medium was supplemented with amino acids or peptides. For B. fibrisolvens strain E14, methionine was identified as the specific growth-limiting amino acid although methionine alone did not support growth in the absence of NH4Cl. For P. ruminicola strain GA33, any individual amino acid other than methionine or cysteine could supplement the medium and support growth. Enzyme assays confirmed a lack of NADH and NADPH-dependent glutamate dehydrogenase (GDH) activities in this strain.

The in vitro uptake and metabolism of peptides and amino acids by five species of rumen bacteria

Streptococcus bovis JB1, Prevotella ruminicola B(1)4, Selenomonas ruminantium Z108, Fibrobacter succinogenes S85 and Anaerovibrio lipolytica 5S were incubated with either 14C-peptides (mol. wt, 200-1000) or 14C-amino acids to compare their rates of uptake and metabolism. In experiment 1, the bacteria were grown and incubated in a complex medium, but no uptake of 14C-labelled substrates occurred. When casein digest was omitted, uptake rates of 14C-peptides were different (P < 0.01) with each species, but nil for 14C-amino acids. In experiment 2, to minimize the effects of non-radiolabelled peptides and amino acids, defined and semi-defined media were used. Patterns of 14C-peptide uptake resembled those of experiment 1. The 5-min rate for Strep. bovis JB1 was almost twice that of P. ruminicola B(1)4, though by 15 min they were similar and threefold greater than other species; that of A. lipolytica 5S was especially low. Incubations with 14C-amino acids resulted in a wide range (P < 0.01) of uptake rates; after 5 min P. ruminicola B(1)4 possessed the lowest and Strep. bovis JB1 the highest, but after 15 min, that of Sel. ruminantium Z108 was even higher. All bacteria, with the exception of P. ruminicola B(1)4, assimilated 14C-amino acids faster (P < 0.01) than 14C-peptides. Only Strep. bovis JB1 and P. ruminicola B(1)4 were capable of extensively metabolizing 14C-peptides, but all five species metabolized 14C-amino acids; there was evidence of substantial degradation and some synthesis. Calculations suggest that peptides could supply up to 43%, and amino acids 62% of the N requirements of rumen bacteria.

Variations in the uptake and metabolism of peptides and amino acids by mixed ruminal bacteria in vitro

Mixed ruminal bacteria, isolated from sheep (Q and W) fed a concentrate and hay diet, were anaerobically incubated with either 14C-peptides or 14C-amino acids. Experiment 1 showed that uptake of both 14C-labeled substrates was rapid, but the rate for amino acids was twofold greater than for peptides (molecular weight, 1,000 to 200) initially but was similar after 10 min. Experiment 2 demonstrated that metabolism was also rapid; at least 90% of either 14C-labeled substrate was metabolized by 3 min. Of the radioactivity remaining in bacteria, approximately 30% was in the form of 14C-amino acids, but only in leucine, tyrosine, and phenylalanine. Supernatant radioactivity was contained only in tyrosine, phenylalanine, and mostly proline for incubations with 14C-amino acids but in up to 10 amino acids when 14C-peptides were the substrates. Short-term incubations (< 5 min; experiment 3) confirmed previous uptake patterns and showed that the experimental system was responsive to substrate competition. Experiment 4 demonstrated that bacteria from sheep Q possessed initial and maximum rates of 14C-amino acid uptake approximately fourfold greater (P < 0.01) than those of 14C-peptides, but with no significant differences (P > 0.1) between four 14C-peptide substrate groups with molecular weights of 2,000 to < 200. By contrast, bacteria from sheep W showed no such distinctions (P > 0.1) between rates for 14C-peptides and 14C-amino acids. Calculations suggested that peptides could supply from 11 to 35% and amino acids could supply from 36 to 68% of the N requirements of mixed ruminal bacteria.(ABSTRACT TRUNCATED AT 250 WORDS)